Detecting ancient life: Investigating the nature and origin of possible stromatolites and associated calcite from a one billion year old lake

Brasier, Alexander T.; Dennis, Paul F.; Still, John; Parnell, John; Culwick, Timothy; Brasier, Martin D.; Wacey, David; Bowden, Stephen; Crook, Simon; Boyce, Adrian J.; Muirhead, David

doi:10.1016/j.precamres.2019.04.025

Cited by 5 publications

(7 citation statements)

References 38 publications

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“…The presence of two populations of disordered carbon (Figure 6b) is in agreement with previous work on the Stoer Group (Brasier et al., 2019; Muirhead et al., 2017), though the G‐bands in this study show considerably broader FWHM, which we attribute to differences in measurement instrumentation. Note that only one kerogenous spectrum (Figure 6) was collected in association with a 1085 cm −1 carbonate peak and could represent biogenic material.…”

Section: Discussionsupporting

confidence: 93%

“…Using micro-Raman spectroscopy on samples from the Stac Fada Member, we identified two carbon-rich phases: (i) crystalline grains of impact diamonds ~2-10 lm in diameter with a peak position of ~1328 cm À1 (Figure 4) and (ii) disseminated heterogeneously distributed disordered carbon, with G-band positions (Brasier et al, 2019;Muirhead et al, 2017). Data from this study are colored brown and data from the literature are in black.…”

Section: Reworking and Alteration Of Carbon Phasesmentioning

confidence: 79%

“…Importantly, a lower volume of pre-impact organic life during the Mesoproterozoic (Brasier et al, 2019;Wellman & Strother, 2015) could mean the volume of carbon-rich impact products may differ significantly between the Stac Fada Member and the much more recent Ries and Kara impact craters, dated at ~14.8 and ~70.3 Ma, respectively, when a more modern biosphere existed (Schmieder et al, 2018;Schwarz et al, 2020;Trieloff et al, 1998). As noted in Shumilova et al (2020), natural diamonds called "karite" are present at the Kara astrobleme, suggesting the conversion of organic life at the time of impact to diamond is possible.…”

Section: Reworking and Alteration Of Carbon Phasesmentioning

confidence: 99%

“…Plot of Raman shift versus full-width at half maximum (FWHM) for the G-band of disordered carbon phases: (a) Data from Gaussian fitting of the G-band for the Stoer Group (closed circles) and specifically the Stac Fada Member (open circles) annotated with sample names. (b) Data from this study plotted against literature data on carbon phases from the Stoer Group(Brasier et al, 2019;Muirhead et al, 2017). Data from this study are colored brown and data from the literature are in black.…”

mentioning

confidence: 99%

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Provenance of altered carbon phases and impact history of the Stac Fada Member, NW Scotland

GOODWIN

Tartèse

Garwood

et al. 2023

Meteorit & Planetary Scien

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The Stac Fada Member (Stoer Group) is a ~1.2 Ga melt‐rich impact breccia preserved and intermittently exposed along the NW coast of Scotland. Using a combination of x‐ray diffraction and micro‐Raman spectroscopy, we identify potential coesite that is spatially associated with micron‐sized diamonds, as well as disordered carbon phases. Comparing the graphite G‐band of disordered carbon phases in the impact breccia to samples from underlying units indicates that most of the carbon in the Stoer Group was ultimately derived from the underlying Lewisian basement. Disordered carbon phases within the Stac Fada Member have been modified by mild heating within a hot ejecta blanket rather than shock pressure. We also report the first evidence for impact diamonds discovered within the Stac Fada Member. These diamonds have an average Raman shift of 1328.5 cm−1 and are present within both the impact breccia and the shocked gneiss clasts that are present in sandstones directly underlying the Stac Fada Member contact, and within sandstone rafts entrapped in the unit. These findings have implications for the timing of deposition of the Stac Fada Member, which must have occurred after ballistic ejection of Lewisian basement clasts during the impact event.

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Section: Discussionsupporting

confidence: 93%

Section: Reworking and Alteration Of Carbon Phasesmentioning

confidence: 79%

Section: Reworking and Alteration Of Carbon Phasesmentioning

confidence: 99%

mentioning

confidence: 99%

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Provenance of altered carbon phases and impact history of the Stac Fada Member, NW Scotland

GOODWIN

Tartèse

Garwood

et al. 2023

Meteorit & Planetary Scien

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“…Grotzinger and Rothman 1996;Allwood et al 2018;Zawaski et al 2020). The presence of ( pseudo)laminations can result from abiotic factors, including a variable energy/sediment supply during deposition and self-organization during crystallization, diagenesis, metamorphism and chemical weathering (Ortoleva 1994;Brasier et al 2017Brasier et al , 2019Allwood et al 2018;Zawaski et al 2020) (Fig. 1a).…”

Section: Pseudomicrobialitesmentioning

confidence: 99%

False biosignatures on Mars: anticipating ambiguity

McMahon

Cosmidis

2021

JGS

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It is often acknowledged that the search for life on Mars might produce false positive results, particularly via the detection of objects, patterns or substances that resemble the products of life in some way but are not biogenic. The success of major current and forthcoming rover missions now calls for significant efforts to mitigate this risk. Here, we review known processes that could have generated false biosignatures on early Mars. These examples are known largely from serendipitous discoveries rather than systematic research and remain poorly understood; they probably represent only a small subset of relevant phenomena. These phenomena tend to be driven by kinetic processes far from thermodynamic equilibrium, often in the presence of liquid water and organic matter, conditions similar to those that can actually give rise to, and support, life. We propose that strategies for assessing candidate biosignatures on Mars could be improved by new knowledge on the physics and chemistry of abiotic self-organization in geological systems. We conclude by calling for new interdisciplinary research to determine how false biosignatures may arise, focusing on geological materials, conditions and spatiotemporal scales relevant to the detection of life on Mars, as well as the early Earth and other planetary bodies.Thematic collection: This article is part of the Astrobiology: Perspectives from the Geology of Earth and the Solar System collection available at: https://www.lyellcollection.org/cc/astrobiology-perspectives-from-geology-of-earth-and-solar-system

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Evolutionary synchrony of Earth’s biosphere and sedimentary-stratigraphic record

Davies

Shillito

Slater

et al. 2020

Earth-Science Reviews

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The landscapes and seascapes of Earth's surface provide the theatre for life, but to what 12 extent did the actors build the stage? The role of life in the long-term shaping of the 13 planetary surface needs to be understood to ascertain whether Earth is singular among known 14 rocky planets, and to frame predictions of future changes to the biosphere. Modern 15 geomorphic observations and modelling have made strides in this respect, but an under-16 utilized lens through which to interrogate these questions resides in the most complete 17 tangible record of our planetary history: the sedimentary-stratigraphic record (SSR). The 18 characteristics of the SSR have been frequently explained with reference to changes in 19 boundary conditions such as relative sea level, climate, and tectonics. Yet despite the fact that 20 the long-term accrual of the SSR was contemporaneous with the evolution of almost all 21 domains of life on Earth, causal explanations related to biological activity have often been 22 overlooked, particularly within siliciclastic strata. This paper explores evidence for the ways 23 in which organisms have influenced the SSR throughout Earth history and emphasizes that 24 further investigation can help lead us towards a mechanistic understanding of how the 2 25 planetary surface has co-evolved with life. The practicality of discerning life signatures in 26 the SSR is discussed by: 1) distinguishing biologically-dependent versus biologically-27 influenced sedimentary signatures; 2) emphasizing the importance of determining relative 28 time-length scales of processes and demonstrating how different focal lengths of observation 29 (individual geological outcrops and the complete SSR) can reveal different insights; and 3) 30 promoting an awareness of issues of equifinality and underdetermination that may hinder the 31 recognition of life signatures. Multiple instances of life signatures and their historic range 32 within the SSR are reviewed, with examples covering siliciclastic, biogenic and chemogenic 33 strata, and trigger organisms from across the spectrum of Earth's extant and ancient life. 34 With this novel perspective, the SSR is recognised as a dynamic archive that expands and 35 complements the fossil and geochemical records that it hosts, rather than simply being a 36 passive repository for them. The SSR is shown to be both the record and the result of long-37 term evolutionary synchrony between life and planetary surface processes. 38 42 precipitation from solution. Where it is tractable, in exposed outcrop, cores or seismic 43 sections, the SSR has immense value as a record of ancient surface processes. It is the 44 primary repository of deep time geochemical and fossil evidence, and the only tangible 45

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Detecting ancient life: Investigating the nature and origin of possible stromatolites and associated calcite from a one billion year old lake

Cited by 5 publications

References 38 publications

Provenance of altered carbon phases and impact history of the Stac Fada Member, NW Scotland

Provenance of altered carbon phases and impact history of the Stac Fada Member, NW Scotland

False biosignatures on Mars: anticipating ambiguity

Evolutionary synchrony of Earth’s biosphere and sedimentary-stratigraphic record

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